Very good game!
I found that some things were not that obvious, and I just clicked everything until it did something. I think it would be a good idea to add some hints or tooltips above things (maybe also an outline) to make it things clear.
It would be nice to upgrade your pickaxe using the coins you get (I'm sorry if this is already in the game, I didn't see it).
Overall, I found the game very relaxing and enjoyable. 😁